Device for solidifying a material web

ABSTRACT

The invention relates to a device for solidifying a material web (F) formed of fibers and/or filaments, said device comprising a screen belt (S) carrying the material web (F), a nozzle beam (D) arranged above the screen belt (S) for subjecting the material web (F) to a pressurized fluid with a plurality of fluid jets (W) arranged in at least one row, and a suction device which is disposed below the screen belt (S), interacts with the nozzle beam (D) and has a suction gap (A). The invention is characterized in that the fluid jets (W) hit the material web (F) in the surface area of the suction gap (A). According to the invention, the fluid application (W) is carried out in the rear section of the suction gap (A) when seen in the conveying direction of the material web (F).

The invention relates to a device for solidifying a material web according to the precharacterizing part of claim 1.

From EP 0 859 076 A2, there is known a device for solidifying the fibers of a material web made of natural and/or synthetic fibers of a random type, wherein a belt-drum type compacting of the fiber web is performed. Said device comprises the following features and respectively is designed in the manner outlined hereunder:

-   -   a first endless belt carrying the fiber web, being guided and         deflected in a tensioned manner between at least two rollers,     -   a permeable needling drum having said endless belt wound around         it,     -   a second endless belt, assigned to the first endless belt and         also being guided in a tensioned manner between at least two         rollers, wherein the working strand of said second endless belt         arranged opposite to the working strand of said first endless         belt is circulating in a driven manner in the same direction as         that of the first endless belt,     -   at the intake side, the two working strands of the two endless         belts are in their longitudinal extension conically oriented to         each other in such a manner that the fiber web (the pre-fleece,         the pile) lying on the working strand of the first endless belt         will be increasingly compacted between the advancing endless         belts,     -   the two endless belts are pressed, by means of two rollers,         against the needling drum so as to be wound around the drum with         a stronger force,     -   between said two rollers, a nozzle beam is directed towards the         fiber web for wetting the same.

The device of this type has the advantage that, between the two endless belts, the pre-nonwoven, i.e. the voluminously advancing fiber sheet, will in a slowly increasing manner and at uniform pressure be compacted from the top toward the bottom without shear stress, and will be wetted on the needling drum only when being held tight between the two endless belts. This construction, however, is complex and too expensive for certain products.

Known from EP 1 126 064 B1 is a device which simplifies the compacting as well as the first wetting of the nonwoven. In this known device, a band-band type compacting is provided, and the device comprises the following features and respectively is designed in the manner outlined hereunder:

-   -   a first endless belt carrying the fiber web, being guided and         deflected in a tensioned manner between at least two rollers,     -   a second endless belt, also being guided in a tensioned manner         between at least two rollers, wherein the working strand of said         second endless belt arranged opposite to the working strand of         said first endless belt is circulating in a driven manner in the         same direction as that of the first endless belt,     -   at the intake side, the two working strands of the two endless         belts are in their longitudinal extension conically oriented to         each other in such a manner that the fiber web lying on the         working strand of the first endless belt will be increasingly         compacted between the advancing endless belts,     -   in a region not supported by a deflection roller, a first nozzle         beam with suction device, provided for wetting the fiber web, is         assigned to the two endless belts circulating with each other.

Due to the technical expenditure, also this construction is too cost-intensive for some products.

DE 10 2005 055 939 B3 shows a nozzle beam for generating fluid jets which serve for solidifying a fiber web. The nozzle beam comprises an exchangeable nozzle beam which includes the discharge openings for the fluid. The discharge openings can be arranged in a row but also in two or more rows extending parallel to each other. The discharge openings have a mutual distance and a diameter which are adapted to the applicational use. As a fluid, one can use pressurized water but, generally, also overheated steam.

It is an object of the present invention to provide a simple device for compacting and first treatment of a pile consisting of fibers and/or filaments.

The above object is achieved by the features defined in the device claim. Advantageous modifications of the invention are indicated in the subclaims.

The invention starts from a device for solidifying a material web formed of fibers and/or filaments, said device comprising a screen belt carrying the material web, a nozzle beam arranged above the screen belt for subjecting the material web to a pressurized fluid in the form of a plurality of fluid jets arranged in at least one row, and a suction device comprising a suction gap, said suction device being disposed below the screen belt and interacting with the nozzle beam, wherein the fluid jets hit the material web in the surface area of the suction gap.

According to the invention, it is provided that the application of fluid is performed in the rear region of the suction gap as viewed in the conveying direction of the material web. The material web, i.e. the fiber and/or filament pile, is not subjected to any mechanical compacting, condensation or guidance until the application of fluid. By the enlarged suction passage area ahead of the fluid beams, the fiber and/or filament pile will be stabilized and—in dependence on the strength of the passing suction—will also be slightly condensed. Further, it is prevented by the invention that the fiber and/or filament pile being moved in the direction of the application of fluid could be buckled by the fluid jets or that folds could be generated on its surface. In this manner, disturbances in the quality of the nonwoven are avoided.

In the way of modifications, the following is provided:

-   -   Application of fluid is performed in the rear quarter of the         suction gap.     -   Above the material web carried by the screen belt, a blowing         device is assigned to the suction device for blowing air onto         the surface of the material web. Thereby, the compacting,         stabilizing effect of the air flowing through the pile of the         material web is increased.     -   The suction device is formed as a chamber connected to a suction         air generator, said chamber being delimited in the transport         direction of the material web by a respective bar made of         plastic.     -   Said blowing device is provided with air conducting elements.     -   Said air conducting elements of the blowing device are         adjustable. As a result, the effect of the blown air, enhancing         the compacting, can be adjusted in dependence on the prevailing         conditions.     -   By the blowing device, the pile of the material web can be         subjected to blown air in the conveying direction with varying         strength. This makes it possible to blow an air flow with a         predetermined strength and direction directly into the region of         the suction gap. A second air flow with a different strength         and/or direction will be applied to the material web in the         region ahead of the suction gap and will stabilize the material         web already before air will pass through it above the suction         gap.     -   The screen belt carrying the material web extends in a linearly         tensioned state, the suction gap being arranged directly below         the screen belt.     -   The screen belt carrying the material web is guided around a         needling drum having a permeable surface, the suction gap         cooperating internally of the needling drum with the bottom side         of said permeable surface.

An embodiment of the invention will be explained hereunder with reference to the drawing.

An endless transport belt S, formed as a screen belt and tensioned in a linear manner about deflection rollers, not shown, carries a material web F comprising fibers and/or filaments, said material web being provided, by a carding or spunbond plant, as an uncondensed pile in a largely unsolidified state and being transported in the direction indicated by the arrow. Above the transport belt S with the material web F, a nozzle beam D is arranged across the width of the material web F, the bottom side of said nozzle beam being provided with a plurality of discharge openings for pressurized fluid. In the present embodiment, the fluid is highly pressurized water, and, correspondingly, the pile of the material web F is subjected to a plurality of water jets W. The lined-up discharge openings for the water jets W are arranged in an exchangeable nozzle strip, not shown. It is also possible to use a nozzle strip comprising discharge openings arranged in a plurality of mutually spaced rows.

Below the transport belt S carrying the material web F, a suction device A is arranged which via a conduit system is connected to a separator AS having a suction ventilator SV disposed downstream of it. Within said separator AS, the water will be separated from the water-air mixture, be removed by the suction pump arranged downstream of the separator and be supplied to a water treatment unit, not shown.

Said suction device A is a chamber extending across the width of transport belt S and delimited in the transport direction of material web F by two bars L1 and L2 made of plastic. On the format edges of material web F, the suction gap formed by said bars L1,L2 is closed. In the Figure, the visual representation of the bars L1,L2 of nozzle beam D and particularly the dimensional relations of the components are rendered in a purely schematic manner.

According to FIG. 1, the suction gap formed by bars L1,L2 has a width b. As viewed in the transport direction of material web F, the nozzle beam D with its water jets W discharged from its bottom side is arranged at an offset in the direction of the rear region of the suction gap in such a manner that the water jets W will enter the suction gap and respectively the material web F not centrally, but closer to the rear bar L2 of the suction gap. In the Figure, the distance of the entrance of the water jets W from the rear bar L2 is marked by c, and the distance from the front bar L1 is marked by a. In accordance with the invention, c is selected to fulfill c<a, wherein b=a+c.

By the asymmetric orientation of the water jets relative to the suction gap (bars L1,L2), the material web F is subjected to a stronger passage of suction in the front region (distance a to bar L1) than in the rear region (distance b to bar L2). This volumetrically stronger passage of suction force through the material web F in the front region (a) has a stabilizing effect on the pile which is running against the water jets W and which thereby is subjected to a compressive force against the transport direction.

The stronger passage of suction force through the pile before the water jets W is effective to avoid a bulging of the pile before the first solidifying by the water jets W. Bulging of the pile can generate irregularities in the product which cause a negative visual appearance, e.g. in the form of sites with excessive density or in the form of clouds, and on the other hand have an adverse effect on the strength of the nonwoven. Ultimately, the bulging could reach such an extent that the pile is caused to contact the nozzle beam D and is damaged. This would cause disturbances and interruptions in the production process.

Not illustrated in the Figure is a further embodiment of the invention wherein, before the nozzle beam D as viewed in the conveying direction of the material web F, a blowing device is arranged for blowing air onto the surface of the material web in the region a of the suction gap.

In a practical example, the material web F to be solidified consisted of a spunbonded nonwoven of polypropylene (PP) with a yarn count of 1.8 den. After laying, the spunbonded nonwoven was merely slightly calendered and subsequently was hydrodynamically treated according to the invention. The water pressure in the first nozzle beam D was 80 bar, and the suction device was subjected to an underpressure of 120 mbar. The suction gap had a width b of 12 mm, and the water jets W had a distance a of 10 mm from the front bar L1 of the suction gap. These measures allowed to perform the first hydrodynamic needling without compacting by use of a noticeably lower pressure, whereby the danger of bulging of the pile was further reduced. As compared to a central orientation of the water jets relative to the suction gap, it was possible to finally produce a distinctly more homogenous nonwoven in a disturbance-free manner.

LIST OF REFERENCE NUMERALS

S screen belt, transport belt

F material web, pile

A suction device, suction gap

L1 bar, front bar

L2 bar, rear bar

AS separator

SV suction ventilator, suction air generator

SP suction pump

D nozzle beam

W water jet, application of fluid

b width of suction gap

a distance of water jet from front bar L1

c distance of water jet from rear bar L2 

1. A device for solidifying a material web formed of fibers and/or filaments, said device comprising a screen belt carrying the material web, a nozzle beam arranged above the screen belt for subjecting the material web to a pressurized fluid in the form of a plurality of fluid jets arranged in at least one row, and a suction device comprising a suction gap, said suction device being disposed below the screen belt and interacting with the nozzle beam, said fluid jets hitting the material web in the surface area of the suction gap, characterized in that the application of fluid (W) is performed in the rear region of the suction gap (A) as viewed in the conveying direction of the material web (F).
 2. The device according to claim 1, characterized in that the application of fluid (W) is performed in the rear quarter of the suction gap (A).
 3. The device according to claim 1, characterized in that the suction device (A) is formed as an open-topped chamber connected to a suction air generator (SV), the top side of said chamber being covered by the screen belt (S) and said chamber being delimited in the transport direction of the material web (F) by a respective bar (L1,L2).
 4. The device according to claim 1, characterized in that, above the material web (F) carried by the screen belt (S), a blowing device is assigned to the suction device for blowing air onto the surface of the material web (F).
 5. The device according to claim 4, characterized in that said blowing device is provided with air conducting elements.
 6. The device according to claim 5, characterized in that said air conducting elements of the blowing device are adjustable.
 7. The device according to claim 4, characterized in that, by the blowing device, the pile of the material web can be subjected to blown air in the conveying direction with varying strength.
 8. The device according to claim 2, characterized in that the suction device (A) is formed as an open-topped chamber connected to a suction air generator (SV), the top side of said chamber being covered by the screen belt (S) and said chamber being delimited in the transport direction of the material web (F) by a respective bar (L1,L2).
 9. The device according to claim 8, characterized in that, above the material web (F) carried by the screen belt (S), a blowing device is assigned to the suction device for blowing air onto the surface of the material web (F).
 10. The device according to claim 9, characterized in that said blowing device is provided with air conducting elements.
 11. The device according to claim 10, characterized in that said air conducting elements of the blowing device are adjustable.
 12. The device according to claim 9, characterized in that, by the blowing device, the pile of the material web can be subjected to blown air in the conveying direction with varying strength.
 13. The device according to claim 2, characterized in that, above the material web (F) carried by the screen belt (S), a blowing device is assigned to the suction device for blowing air onto the surface of the material web (F).
 14. The device according to claim 13, characterized in that said blowing device is provided with air conducting elements.
 15. The device according to claim 14, characterized in that said air conducting elements of the blowing device are adjustable.
 16. The device according to claim 13, characterized in that, by the blowing device, the pile of the material web can be subjected to blown air in the conveying direction with varying strength.
 17. The device according to claim 3, characterized in that, above the material web (F) carried by the screen belt (S), a blowing device is assigned to the suction device for blowing air onto the surface of the material web (F).
 18. The device according to claim 17, characterized in that said blowing device is provided with air conducting elements.
 19. The device according to claim 18, characterized in that said air conducting elements of the blowing device are adjustable.
 20. The device according to claim 17, characterized in that, by the blowing device, the pile of the material web can be subjected to blown air in the conveying direction with varying strength. 